[PATCH 5/5] ACPI / scan: Add second pass to acpi_bus_trim()

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Make acpi_bus_trim() work in analogy with acpi_bus_scan() and carry
out two passes such that ACPI drivers will be detached from device
nodes being removed in the first pass and the device nodes themselves
will be removed in the second pass.

For this purpose split the driver unregistration out of
acpi_bus_remove() into a new routine, acpi_bus_device_detach(), that
will be executed by acpi_bus_trim() in the additional first pass as
a post-order callback.

This is necessary, because some ACPI drivers' .remove() routines
unregister struct device objects associated with the ACPI device
nodes being removed and that needs to happen while the ACPI
device nodes are still around (for example, in case they need to be
used for power management or similar things at that time).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/scan.c |   44 ++++++++++++++++++++++++++++----------------
 1 file changed, 28 insertions(+), 16 deletions(-)

Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1425,22 +1425,6 @@ static void acpi_device_set_id(struct ac
 	}
 }
 
-static acpi_status acpi_bus_remove(acpi_handle handle, u32 lvl_not_used,
-				   void *not_used, void **ret_not_used)
-{
-	struct acpi_device *dev = NULL;
-
-	if (acpi_bus_get_device(handle, &dev))
-		return AE_OK;
-
-	dev->removal_type = ACPI_BUS_REMOVAL_EJECT;
-	device_release_driver(&dev->dev);
-
-	acpi_device_unregister(dev);
-
-	return AE_OK;
-}
-
 void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 			     int type, unsigned long long sta)
 {
@@ -1647,8 +1631,36 @@ int acpi_bus_add(acpi_handle handle)
 }
 EXPORT_SYMBOL(acpi_bus_add);
 
+static acpi_status acpi_bus_device_detach(acpi_handle handle, u32 lvl_not_used,
+					  void *not_used, void **ret_not_used)
+{
+	struct acpi_device *device = NULL;
+
+	if (!acpi_bus_get_device(handle, &device)) {
+		device->removal_type = ACPI_BUS_REMOVAL_EJECT;
+		device_release_driver(&device->dev);
+	}
+	return AE_OK;
+}
+
+static acpi_status acpi_bus_remove(acpi_handle handle, u32 lvl_not_used,
+				   void *not_used, void **ret_not_used)
+{
+	struct acpi_device *device = NULL;
+
+	if (!acpi_bus_get_device(handle, &device))
+		acpi_device_unregister(device);
+
+	return AE_OK;
+}
+
 int acpi_bus_trim(struct acpi_device *start)
 {
+	/* Detach all ACPI drivers from the device nodes being removed. */
+	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
+			    acpi_bus_device_detach, NULL, NULL);
+	acpi_bus_device_detach(start->handle, 0, NULL, NULL);
+	/* Remove the device nodes. */
 	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
 			    acpi_bus_remove, NULL, NULL);
 	acpi_bus_remove(start->handle, 0, NULL, NULL);